June 3 is the predictable day when the South West Monsoon hits the Kerala coast. Despite a delay of three days, the India Meteorological Department (IMD) says that there is nothing to worry, as the country will receive normal to above normal rainfall this SW monsoon season, which is much crucial for the country’s agriculture and economy. The SW Monsoon generally hits the Kerala coast on June 1.
The IMD said that Monsoon (June to September) rainfall over the country as a whole is likely to be 101 per cent of Long Period Average (LPA). The Met department had earlier predicted the onset of Monsoon on May 31. However, they revised the date to June 3 as the progress of the Monsoon halted because of the weak South Westerly winds due to the eastward progression of the Madden-Jullian Oscillation (MJO).
Noting that the Monsoon 2021 would be slightly wetter, the IMD said above normal rainfall probability is likely over most areas of eastern parts of central India, along the planes of Himalayas and east India. Below normal probability is likely over many areas of northwest India and southern parts of south peninsula and some areas of northeast India.
As per the IMD update, the monsoon rain forecast over the four homogeneous regions of India is as follows:
- Northwest India: Normal (92-108%)
- South Peninsula: Normal (93-107%)
- East and Northeast India: Below normal
- Central India: Above normal ( 106%)
Sea Surface Temperature (SST) Conditions
La Niña conditions which peaked in November last year, started weakening in the early part of 2021 and turned into neutral ENSO conditions by end of April 2021. Presently, neutral ENSO conditions are seen over the equatorial Pacific along with substantially warmer subsurface temperatures over the region. Atmospheric patterns also reflect neutral ENSO conditions. The latest MMCFS and other global model forecast indicate that neutral ENSO conditions will continue during the upcoming monsoon season. At present, neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. The latest forecast from the MMCFS and other global models together indicate possibility of development of negative IOD conditions during the monsoon season.
Multi Model Ensemble (MME) Forecasting System
The IMD said that the updated MME forecast for 2021 southwest Monsoon season rainfall has been computed using various coupled global model forecasts with May initial conditions. Climate models with the highest forecast skills over the Indian monsoon region including MMCFS have been used to prepare the MME forecast, the IMD said.
The rain in the south-west monsoon season begins abruptly. The sudden outburst of the moisture-laden winds associated with violent thunder and lightning is often termed as the “break” or “burst” of the monsoons. The Monsoon enters the Indian Coast by June 1, with a of variation of a week. It reaches the interior parts of the country by July first week. The entire subcontinent comes under the grip of Monsoon by mid-July. The monsoon approaches the landmass in two branches namely Arabian Sea branch and the Bay of Bengal branch.